1. Technical Field
The present disclosure relates to a surgical apparatus for laparoscopic and endoscopic procedures. In particular, the disclosure relates to a surgical apparatus having a locking mechanism for maintaining a remotely-actuated component of the instrument at a particular position or orientation.
2. Background of Related Art
Typically in a laparoscopic, an endoscopic, or other minimally invasive surgical procedure, a small incision or puncture is made in a patient's body. A cannula is then inserted into a body cavity through the incision, which provides a passageway for inserting various surgical devices such as scissors, dissectors, retractors, or similar instruments. To facilitate operability through the cannula, instruments adapted for laparoscopic surgery typically include a relatively narrow shaft supporting an end effector at its distal end and a housing at its proximal end. Arranging the shaft of such an instrument through the cannula allows a surgeon to manipulate actuators on the housing from outside the body to induce the end effector to carry out a surgical procedure at a remote internal surgical site. This type of laparoscopic procedure has proven beneficial over traditional open surgery due to reduced trauma, improved healing and other attendant advantages.
A steerable laparoscopic or endoscopic instrument may provide a surgeon with a range of operability suitable for a particular surgical procedure. For example, the instrument may be configured such that the end effector may be aligned with a longitudinal axis of the instrument to facilitate insertion through a cannula, and thereafter, the end effector may be caused to articulate or move off-axis as necessary to appropriately position the end effector to engage tissue. Some mechanisms for articulating the distal end of an endoscopic instrument include a pair of tension-bearing drive cables, or other tensile members with distal ends anchored to the articulating portion on opposite sides of an instrument axis. The proximal ends of the drive cables are operatively coupled to an actuator on the housing that is responsive to manipulation by the surgeon to draw one of the drive cables proximally while simultaneously permitting distal motion in the other drive cable. This motion in the drive cables induces pivotal motion of the distal end of the instrument.
When the end effector of a steerable, articulating instrument has been satisfactorily positioned and oriented, a surgeon may maintain the position and orientation of the end effector by continuously exerting the necessary forces at the housing. Alternatively, some instruments are provided with a locking mechanism that permits the surgeon to temporarily lock the orientation of the end effector so that a continuous exertion of force at the housing is not required. For example, commonly owned U.S. patent application Ser. No. 12/609,477 describes a locking collar in the housing of an instrument that is movable to selectively lock and unlock distal articulating movement of an end effector. The locking collar described is movable into, and out of contact with a sphere in the housing. The sphere is coupled to a set of tension-bearing articulation cables and is arranged to pivot to induce the distal articulating motion. A frictional force is generated in the housing when the locking collar engages the sphere to thereby maintain the articulated position of the instrument.
When tensile members are employed to induce movement at the distal end of an instrument, the tensile members themselves may be engaged to generate a frictional force that may be used to lock or impede the distal motion. Mechanisms for engaging a tension-bearing cable have been developed for other industries such as architecture or construction, and include applications such as wall retainers, concrete reinforcement and cable stay or suspension bridges. Typically these mechanisms are employed to retain an appropriately tensioned cable. One type of cable engaging mechanism is described in the background section of U.S. Pat. No. 7,726,082. The mechanism described includes a retaining wedge that has a conical-exterior shape that fits into a mating, tapered opening in an anchor plate. The retaining wedge is divided into circumferential segments that permit the retaining wedge to be installed around a cable such that an interior surface of the retaining wedge grips the cable. A tensioning device is employed to apply a tension to the cable, and when the tensioning device is released, the cable tends to draw the retaining wedge into the anchor plate. The tapered opening of the anchor plate tends to compress the circumferential segments onto the cable, and the cable is thereby retained.
A retaining wedge or collet may be employed to engage a tensile member in the locking mechanism of a surgical instrument. In such an application, the motion at the distal end of the instrument may be selectively and temporarily impeded.